pep-gprs.c

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/*
 * File: pep-gprs.c
 *
 * GPRS over Phonet pipe end point socket
 *
 * Copyright (C) 2008 Nokia Corporation.
 *
 * Author: Rémi Denis-Courmont
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/if_ether.h>
#include <linux/if_arp.h>
#include <net/sock.h>

#include <linux/if_phonet.h>
#include <net/tcp_states.h>
#include <net/phonet/gprs.h>

#define GPRS_DEFAULT_MTU 1400

struct gprs_dev {
    struct sock     *sk;
    void            (*old_state_change)(struct sock *);
    void            (*old_data_ready)(struct sock *, int);
    void            (*old_write_space)(struct sock *);

    struct net_device   *dev;
};

static __be16 gprs_type_trans(struct sk_buff *skb)
{
    const u8 *pvfc;
    u8 buf;

    pvfc = skb_header_pointer(skb, 0, 1, &buf);
    if (!pvfc)
        return htons(0);
    /* Look at IP version field */
    switch (*pvfc >> 4) {
    case 4:
        return htons(ETH_P_IP);
    case 6:
        return htons(ETH_P_IPV6);
    }
    return htons(0);
}

static void gprs_writeable(struct gprs_dev *gp)
{
    struct net_device *dev = gp->dev;

    if (pep_writeable(gp->sk))
        netif_wake_queue(dev);
}

/*
 * Socket callbacks
 */

static void gprs_state_change(struct sock *sk)
{
    struct gprs_dev *gp = sk->sk_user_data;

    if (sk->sk_state == TCP_CLOSE_WAIT) {
        struct net_device *dev = gp->dev;

        netif_stop_queue(dev);
        netif_carrier_off(dev);
    }
}

static int gprs_recv(struct gprs_dev *gp, struct sk_buff *skb)
{
    struct net_device *dev = gp->dev;
    int err = 0;
    __be16 protocol = gprs_type_trans(skb);

    if (!protocol) {
        err = -EINVAL;
        goto drop;
    }

    if (skb_headroom(skb) & 3) {
        struct sk_buff *rskb, *fs;
        int flen = 0;

        /* Phonet Pipe data header may be misaligned (3 bytes),
         * so wrap the IP packet as a single fragment of an head-less
         * socket buffer. The network stack will pull what it needs,
         * but at least, the whole IP payload is not memcpy'd. */
        rskb = netdev_alloc_skb(dev, 0);
        if (!rskb) {
            err = -ENOBUFS;
            goto drop;
        }
        skb_shinfo(rskb)->frag_list = skb;
        rskb->len += skb->len;
        rskb->data_len += rskb->len;
        rskb->truesize += rskb->len;

        /* Avoid nested fragments */
        skb_walk_frags(skb, fs)
            flen += fs->len;
        skb->next = skb_shinfo(skb)->frag_list;
        skb_frag_list_init(skb);
        skb->len -= flen;
        skb->data_len -= flen;
        skb->truesize -= flen;

        skb = rskb;
    }

    skb->protocol = protocol;
    skb_reset_mac_header(skb);
    skb->dev = dev;

    if (likely(dev->flags & IFF_UP)) {
        dev->stats.rx_packets++;
        dev->stats.rx_bytes += skb->len;
        netif_rx(skb);
        skb = NULL;
    } else
        err = -ENODEV;

drop:
    if (skb) {
        dev_kfree_skb(skb);
        dev->stats.rx_dropped++;
    }
    return err;
}

static void gprs_data_ready(struct sock *sk, int len)
{
    struct gprs_dev *gp = sk->sk_user_data;
    struct sk_buff *skb;

    while ((skb = pep_read(sk)) != NULL) {
        skb_orphan(skb);
        gprs_recv(gp, skb);
    }
}

static void gprs_write_space(struct sock *sk)
{
    struct gprs_dev *gp = sk->sk_user_data;

    if (netif_running(gp->dev))
        gprs_writeable(gp);
}

/*
 * Network device callbacks
 */

static int gprs_open(struct net_device *dev)
{
    struct gprs_dev *gp = netdev_priv(dev);

    gprs_writeable(gp);
    return 0;
}

static int gprs_close(struct net_device *dev)
{
    netif_stop_queue(dev);
    return 0;
}

static netdev_tx_t gprs_xmit(struct sk_buff *skb, struct net_device *dev)
{
    struct gprs_dev *gp = netdev_priv(dev);
    struct sock *sk = gp->sk;
    int len, err;

    switch (skb->protocol) {
    case  htons(ETH_P_IP):
    case  htons(ETH_P_IPV6):
        break;
    default:
        dev_kfree_skb(skb);
        return NETDEV_TX_OK;
    }

    skb_orphan(skb);
    skb_set_owner_w(skb, sk);
    len = skb->len;
    err = pep_write(sk, skb);
    if (err) {
        LIMIT_NETDEBUG(KERN_WARNING"%s: TX error (%d)\n",
                dev->name, err);
        dev->stats.tx_aborted_errors++;
        dev->stats.tx_errors++;
    } else {
        dev->stats.tx_packets++;
        dev->stats.tx_bytes += len;
    }

    netif_stop_queue(dev);
    if (pep_writeable(sk))
        netif_wake_queue(dev);
    return NETDEV_TX_OK;
}

static int gprs_set_mtu(struct net_device *dev, int new_mtu)
{
    if ((new_mtu < 576) || (new_mtu > (PHONET_MAX_MTU - 11)))
        return -EINVAL;

    dev->mtu = new_mtu;
    return 0;
}

static const struct net_device_ops gprs_netdev_ops = {
    .ndo_open   = gprs_open,
    .ndo_stop   = gprs_close,
    .ndo_start_xmit = gprs_xmit,
    .ndo_change_mtu = gprs_set_mtu,
};

static void gprs_setup(struct net_device *dev)
{
    dev->features       = NETIF_F_FRAGLIST;
    dev->type       = ARPHRD_PHONET_PIPE;
    dev->flags      = IFF_POINTOPOINT | IFF_NOARP;
    dev->mtu        = GPRS_DEFAULT_MTU;
    dev->hard_header_len    = 0;
    dev->addr_len       = 0;
    dev->tx_queue_len   = 10;

    dev->netdev_ops     = &gprs_netdev_ops;
    dev->destructor     = free_netdev;
}

/*
 * External interface
 */

/*
 * Attach a GPRS interface to a datagram socket.
 * Returns the interface index on success, negative error code on error.
 */
int gprs_attach(struct sock *sk)
{
    static const char ifname[] = "gprs%d";
    struct gprs_dev *gp;
    struct net_device *dev;
    int err;

    if (unlikely(sk->sk_type == SOCK_STREAM))
        return -EINVAL; /* need packet boundaries */

    /* Create net device */
    dev = alloc_netdev(sizeof(*gp), ifname, gprs_setup);
    if (!dev)
        return -ENOMEM;
    gp = netdev_priv(dev);
    gp->sk = sk;
    gp->dev = dev;

    netif_stop_queue(dev);
    err = register_netdev(dev);
    if (err) {
        free_netdev(dev);
        return err;
    }

    lock_sock(sk);
    if (unlikely(sk->sk_user_data)) {
        err = -EBUSY;
        goto out_rel;
    }
    if (unlikely((1 << sk->sk_state & (TCPF_CLOSE|TCPF_LISTEN)) ||
            sock_flag(sk, SOCK_DEAD))) {
        err = -EINVAL;
        goto out_rel;
    }
    sk->sk_user_data    = gp;
    gp->old_state_change    = sk->sk_state_change;
    gp->old_data_ready  = sk->sk_data_ready;
    gp->old_write_space = sk->sk_write_space;
    sk->sk_state_change = gprs_state_change;
    sk->sk_data_ready   = gprs_data_ready;
    sk->sk_write_space  = gprs_write_space;
    release_sock(sk);
    sock_hold(sk);

    printk(KERN_DEBUG"%s: attached\n", dev->name);
    return dev->ifindex;

out_rel:
    release_sock(sk);
    unregister_netdev(dev);
    return err;
}

void gprs_detach(struct sock *sk)
{
    struct gprs_dev *gp = sk->sk_user_data;
    struct net_device *dev = gp->dev;

    lock_sock(sk);
    sk->sk_user_data    = NULL;
    sk->sk_state_change = gp->old_state_change;
    sk->sk_data_ready   = gp->old_data_ready;
    sk->sk_write_space  = gp->old_write_space;
    release_sock(sk);

    printk(KERN_DEBUG"%s: detached\n", dev->name);
    unregister_netdev(dev);
    sock_put(sk);
}